Fluorescent lamp starter



Dec 27 i949" J. P. HUNTER 2,492,750

FLUORESCENT LAMP STARTER Filed aan. 1s, 1947 Invent o1- James P. Hunter,

b3 www His Atorweg.

Patented Dec. 27, 1949 James P. Hunter.. Stratford.. Conn. assigner toGeneral.' Electric Company, a. corporation of NexviYnrk" 18,1947;,.SerialN01- 722.8251

I Cl'ai'm. (Cl. 17d-320).'

The present. invention.r` te apparatus for startingv fluorescent lampsl1particiilarlyy lamps having at least one electron emitting. cathode.

Starters. for fluorescent.lampsasheretofore-proposed.- includea.switcmwhiclr may be. ot the. glow tube type, for openingthe circuitt theelectron emitting. cathode so..- that a..leighyoltagev impressed acrossthe. lampy from. aballast device to start the arc. inthef lamp. In.other prior. arc starters, the starting switch unit: includes. not onlythe. startingswitclrbut also aloekoutswitch by which the startingswitch.is.rendered. inoperative after it has.A madea,y number ofunsuccessful attempts. to start the lamp. In some; casesl the lockoutswitchv is; manually reset.. but. in:y others: it is automaticallyresets Theliockautfswitch mechanismusually includes athermal elementsuch. as a bi-metallic strip carryineacontact--which coopcrates with.afixed Contact.. If theilamp, fails to start, the. twov contacts areseparated by the,y bi.- metal-licv strip whichA is heated.. locallysupplied heat produced by theiiow of. current1 throughy a resistor.

It is an:` object ofv my invention toN provide` an improved automatic.4reset starter whichlisvinexpensive to manufacture, and. extremely:accurate and reliable inA operation.

The above and.4 other objects of invention will best be. understoodffromthe followingidescription taken in.Y connection. with.- the.accompanying drawing in which. Fig.. l. showssa complete starter infront elevation.. withT the.. enclosingA can' in.v seetion; Fig. 2 showsan end elevation of the device showninzf Fig. 1;; Figtr is a rearelevation of the device shown in Fig. 1; Fig. 4 is a section taken alongthe line; [-4I.irrEig;. It. andF'g. 5 is a schematic element and circuitdiagram ot the starter according to my invention.

As shown on the drawing, the starting device comprises asuitableenclosing can Ii, closed at the bottom by a plate of. insulatingmaterial. 2 in which. are mounted connection pins. 3= and 4 whereby the`device is connectedlinto circuitwith the fluorescent lamp 5'.Perpendicnlarly mounted on the basel is a supportAB'oiinsulatingrmaterial. On one side of the supportrtheref are mounted.a starting glow switch 'IQ andv a: capacitor 8l. An L-shaped.birmetallic strip 9 is also mounted;A on the support by means of-` tworivets IIL` and. I-I passing through holes in one-arm. of thef. L.. Theother arm of the elemente' ishorizontally disposed and, is free to bendand tomove perpendicularly tothe plane of the.- support 6. For thispurpose apart of the upper portion ot the sup.- port G is cut away asshowninEig. 3. At the free end of the element 9 there'is secured acontact element; I2, preferably off a.: precious metal; such as silver.which may beim firm a.. short piece of wire secured to the bi-metallicelement 9 by spot welding. The contact I2 is arranged 2; to. cooperatewith` asimilar contactv I3 secured. to the main loi-metallic thermalmmember I-t which ismountedon the-opposite sidefof. the supporting plate.G. as by'rivet. I5. and-by rivetZIl.

The bi-metallic element Ill is. primarily actu.- atedy by heat-vgenerated by a low ohmic. resistor Iwhich may be of the kind described.inPatent No. 2,391,680 of Leonard Wl` Cook, issuedDecember 25 1.945, andvassigned toA thesame= assignee as the present application. As.described. in-v that patent, the resistor L6. may comprise. a low ohmicresistance coil wound on a-core of low heatconductivi-ty which isconnectedto the-thermal mem.- ber by a member having good. heatconductivity and which provides a restricted path forl the transfer ofheat from.` the core to the thermal member. This thermal conducting.member is shown in- Fg. 3 at I'I..

The thermalv element I4 may further be oper.- ated.v by heat produced bya holdouty heater I8 which. comprises.v a high ohmic resistance. device.According to my invention I prov-ide for direct thermal` conduction ofthel heat produced.` by the resistor I8-to the; thermal. element. I4 atthe rivet ZIJ.V To this end I prefer to make.- the resistor I8 of.carbonzor other high resistance'heating material with. highly thermallyconductive. metal leads one ofwhich serves as a metallic heat conductingelement. t9 which is welded. orsoldered. to the element Ity at the rivet2li or is. otherwise secu-red tothe element I-t toprovide goodthermalconductivity between the resistor I8 and the thermal element' If. Thislead I9 is very short which resultsi-n highconductivey eflcency'sincelittle heat is dissipated by air conductioncr radiation.

shownl in Figures. 2; 3 and 4 of the drawing; the lead I9.- is notisubstantially longer than the resistors diameter. Thethermalconductingelement Ill.` simultaneously'. serves to. make-- an electricalconnection between the'resistor.v IVI? and the thermal.rv element I 4iThe electrical connections: of; the various.. elementsv are. showniri'iig; 5. and the operationV of the device will be clear therefrom.When the line switch is closed;y current will initially. 'ow through:the first. lamentin theiiuorescent lamp 5I through` the: glow switch 1;.through. the bimetallic. strip 9;. the'. cooperating: contactsr I2" andlf3 which are normally` closed; .thefbi-metallc vstrip I4;,. resistornI6., thev second lamentz of the; lamp 5, to the other side of; thelin'e;After a predetermined; period. of time.. the resistor t6. producessuflici'enti heat.v which. is. conducted through. the conducting'member`I7" to thea biemetallic strip I4, tm cause' the strip- I4toxdei'ectcontact. l3-r awayfrom` contact I2; thereby. opening thestarting circuit. Normally, the arein-` the lamp 5I. will` then startunder the. influenceV of thefhighvoltage-producedby the ballast in.I thecircuit.. however; the lamp fails to start the bi-metallic strip I4 willcool again, thereby closing contacts I2 and I3 to repeat the startingcycle. It will be observed that while contacts I2 and I3 are open andthe lamp has not started, substantially full line .voltage appearsacross the high resistor I8. After several starting cycles during whichthe lamp has failed to start, suflicient heat will be produced by theresistor I8 to maintain the bi-metallic element I4 continuously in aexed position after the heat from resistor I6 once opens the contacts,thereby continuously keeping contacts I2 and I3 open and preventingreoccurrence of the starting cycle. This condition will persist untilthe defective lamp is removed from the circuit and a new lamp issubstituted or the line switch is opened.

Since the resistor I8 is always across the line while there is adefective lamp in the circuit and the line switch is closed, there willbe a continuous current flowing in the circuit. In order to make theenergy loss small, it is, therefore, important to make as eicient use aspossible of the heat generated by the resistor I8, This aim is achievedby my arrangement of providing direct thermal conduction between theresistor I8 and the thermal element I4.

The use of the direct thermal conduction element I9 has anotheradvantage which makes possible an improved accuracy in the operation ofmy starter. 'I'his consists in making possible the elimination of bendsor corrugations in the bimetallic strip I4 which, it will be noted, is asimple hat strip not formed in any way. By the avoidance of all bending,no stresses are set up in the bi-metallic strip. I have found that as aconsequence the amount of deflection of the strip for a given amount oftemperature change is substantially constant. Another advantage ofmaking the thermal element I4 in the form of a straight strip ofbi-metal is that each strip in routine manufacture will be found to bethe same within very close tolerances so that individual calibration ofthese elements is not required in order to attain the desired accuracyof operation.

In order further to secure accurate operation in spite of ambienttemperature changes, I have provided a compensating bi-metallic strip 9which carries the contact I2 which cooperates with the contact I3 on themain bi-metallic strip I4. The main bi-metallic strip I4 is intended tobe deilected only by reason of locally generated heat produced by theresistors I6 and I8. It will, however, in a slight measure deflect inresponse to ambient temperature changes. While such deiiection might notbe suiiicient to open contacts I2 and I3 even with contact I2 firmlyfixed, such ambient temperature deflection tends toproduce a variationin the contact pressure which in turn tends to give rise to aninaccuracy in the operation of the starter. My invention avoids this byproviding the compensating bi-metallic strip 9, which is, of course,subjected to the same ambient temperature as the main bi-metallic stripI4. Therefore, the contact I2 will be moved in the same direction as thecontact I3 is moved by the element I4 in response to ambient temperaturechanges. It is important in this connection to note the two pointanchorage of the compensating loi-metallic strip 9. This anchorageprovides the necessary rigidity so that the position of the element 9will not change with time or due to softening of the supporting member 6on account of heat which may eventually be developed within thecontainer I. It is also important to note that the compensating bi-metalis on the opposite 4 side of the support from the actuating bi-metal andthe local heaters. The compensating bimetal is thus shielded ...from theheat of the resistors and is only affected by ambient temperature.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

An automatic reset starter for fluorescent lamps comprising a base, aninsulating support mounted thereon, first and second terminals mountedon said base and adapted for connection in circuit with the lamentaryelectrodes of a hot cathode iiuorescent lamp, a bi-metallic stripsecured by one end on said support, a movable contact on the free end ofsaid strip, aA cooperating contact supported from said support, a glowswitch connested between said cooperating contact and said firstterminal, a low resistance time delay heater for heating said strip toopen said contacts after a predetermined period of energization of saidelement, said low resistance heater being electrically connected to saidsecond terminal and connected to the secured end of said strip byelectrically and thermally conductive means, a high resistance lock-outheater for heating said strip to hold said contacts open, said highresistance heater being electrically connected by one lead to said stripbetween said low resistance heater connection and said movable contactand electrically connected by its other lead to said rst terminal,whereby upon the opening of said contacts, said high resistance heateris connected in series with said low resistance heater, said highresistance heater comprising a carbon resistor element having metallic,thermally conductive wire leads in the ends thereof, the said one ofwhich is not substantially longer than the diameter of the element andis fused at its free end directly tol said strip for providing a directheat conductive connection therewith, the electrical connections to theother lead of said element comprising electrical conductors of lowerthermal capacity than the thermal capacity of said strip, and saidelement being mounted on said support at an'angle to-said strip andextending away from said support, whereby heat transfer from saidelement to said strip is principally through said one lead.

JAMES P. HUNTER.

REFERENCES CITED The following references are of record in the filevofthis patent:

UNTTED vsTATEs PATENTS Number Name Date 2,128,869 Winborne Aug. 30, 19382,294,191 Lord Aug. 25, 1942 2,313,745 Hays Mar. 16,1943 2,332,492Bensin Oct. 19, 1943 2,333,215 Thomas Nov. 2, 1943 2,341,905 Cook Feb.15, 1944 2,343,172 Cook Feb. 29, 1944 2,343,262 McCarthy Mar. 7, 19442,346,109 McCarthy Apr. 4, 1944 2,352,713 Hodgkins July 4, 19442,352,940 Cook July 4, 1944 2,355,476 Smith et al Aug. 8, 1944 2,391,680Cook Dec. 25, 1945 FOREIGN PATENTS Number Country Date Great BritainNov. 19, 1925

